In electrocardiography, the so-called QRS-onset, or Q-onset, in each cardiac-beat, or cardiac cycle, marks the start of electrical depolarization of the heart ventricles. In the context of correlated electroacoustic cardiography, this well-recognized QRS-onset (or Q-onset, a term which is used herein interchangeably with QRS-onset) fiducial is important as a reference for computing the respective durations of a number of important heart-functionality time intervals, such as the electromechanical activation time interval (EMAT) between Q-onset and the closure of the mitral valve. In fact, and as those skilled in the art well know, one of the most important measurements which is relied upon in terms of assessing a person's heart functionality is this EMAT time interval, also referred to as the QS1 time interval—the time interval between Q-onset and the occurrence of the first heart sound (S1). Accordingly, accurate determination of the time of Q-onset in each cardiac cycle is extremely critical to heart-behavior assessment.
In circumstances where a pacemaker is in place in a subject, Q-onset presence and timing confusion can occur. For example, if a particular cardiac cycle is in fact initiated by a ventricular pacemaker impulse, referred to as a pacer spike, rather than by an intrinsic (anatomical) Q-onset event, then the onset of depolarization is best represented by the occurrence time of such a pacer spike. Knowing what is the truth about the time-initiation of depolarization onset is, of course, mandatory for achieving measurement accuracy based upon this initiation event, and so it is very important to distinguish these two different kinds of depolarization-initiation events so as to identify clearly what event to select as the one representing true Q-onset. Put another way, and as those skilled in the art well recognize, where a pacemaker is present, one cannot simply rely on pacemaker-activity output to describe, with confident accuracy, the reality of Q-onset, because of the fact that the relevant pacemaker (a) may be out of synchronization, (b) may possibly be an atrial rather than a ventricular pacemaker, and (c) if it is a bi-ventricular pacemaker, there must be some way of identifying which heart chamber is specifically associated with pacemaker activity.
In this setting, accordingly, the present invention is concerned particularly with identifying, with as much accuracy as possible, the time, during each heartbeat, of true Q-onset. In a more particular sense, the present invention is concerned with clearly identifying this Q-onset event in a circumstance where a subject is equipped with a pacemaker whose pacing pulses may (but not necessarily so) be the true indicators of Q-onset.
In relation to the preferred and best-mode manner of practicing the present invention, which includes algorithmically programmed computer processing, there are several categories of ECG and pacemaker information which are especially relevant. These categories define the key pieces of input information which, for a selected, predetermined time span (such as about 10-seconds), which includes a number—a collection—of successive cardiac cycles, are gathered/obtained and supplied to what is referred to herein as a Q-Onset Selection block which, essentially, takes the form of at least a portion of an appropriately algorithmically programmed digital computer that forms one of the central operational systemic “components” of the invention. It is by the operation of this block that an accurate assessment of Q-onset is made.
Such input information supplied to this block preferably includes conventional, multi-lead (such as 12-lead, though a lesser number of leads may be employed if desired) ECG information which also carries accompanying information defining, for each cardiac cycle in the collection of the mentioned number of gathered, successive cardiac cycles, the time locations of conventionally detected (intrinsic) Q-onset events and of pacemaker spike events. Another piece of input information is derived directly from a selected, single ECG lead, such as the so-called V-4 ECG lead. Also supplied to the Q-Onset Selection block is information specifically relevant to pacemaker, or pacer, operation, derived synchronously from the just-mentioned, conventionally acquired ECG information. This pacemaker-operation information specifically includes pacer spike information in terms of the time occurrences of pacer spikes, as well as their types, i.e., as being either atrial, ventricular, first bi-ventricular, or second bi-ventricular, and more broadly speaking as being either ventricular or bi-ventricular.
Still a further piece of information which is relevant, and which may be supplied by the same equipment and methodology which supplies the mentioned, conventionally acquired ECG information, is a characterization of the types of heartbeats, or cardiac cycles, which have been detected during the above-mentioned, predetermined time span. In this regard, there are recognized, for the purpose of the description of the present invention, to be two, different, so-called cardiac cycle types, one of which is referred to as being an intrinsically, or internally (i.e., by the anatomy), initiated cardiac cycle, and the other of which is referred to as being a pacer-spike-initiated cardiac cycle.
With such input information, the Q-onset selection activity of the invention functions to produce, among other things as reportable output information, the relevant, confirmation, Q-onset timing and identity output information. This output information fundamentally, and variously, defines, for each cardiac cycle involved in an investigation, (a) the times within these cycles of “best-determined” Q-onset, (b) the identifying class (per cycle) of the associated, selected, Q-onset event as being either an intrinsic event or a pacer event, and (c) the associated cycle class-identity (intrinsic or pacer).
In general terms, such Q-onset selection, per cardiac cycle, uniquely involves (1) during a predetermined time span which includes a plurality of successive, QRS cardiac cycles, gathering both ECG and pacemaker-spike information for, and within, each such cycle, (2) with respect to each such gathered cardiac cycle, time-locating, identifying and time-position sorting, first to last, each intrinsic Q-onset and each pacemaker-spike event, including specifically identifying each pacemaker-spike event as being one of ventricular or bi-ventricular, (3) also with regard to each such cardiac cycle, evaluating, with respect a single, selected, QRS waveform, the waveform slope therein from (a) a time just preceding, to (b) a time just following, the mentioned, time-position sorted, first-in-time and last-in-time one of such time-located, identified and sorted events, respectively, (4) from the mentioned slope evaluating practice, finding the time, in the mentioned, single, selected QRS-waveform, of the first substantial QRS-waveform slope change, (5) in each cardiac cycle, selecting to be the correct Q-onset therein the time-sorted event in that cycle whose time position most immediately precedes the time of the mentioned, found, first-substantial slope change, and (6) with respect to each cardiac cycle, maintaining the identity of the selected to-be-correct Q-onset event.
Such Q-onset determination is followed, among other things, by appropriate presenting and/or reporting of the determination outcome so as to enable thereafter, and as an illustration of special utility, accurate calculation of the kinds of important heart-functionality time intervals, like the EMAT interval mentioned earlier herein.
These and other features, advantages and reportable Q-onset outcomes which are offered by the present invention will become more fully apparent as the detailed description of the invention which follows below is read in conjunction with the accompanying drawings. This detailed invention description is specifically presented in block/schematic structural and methodologic drawings, and in text terminology, both very familiar to those generally skilled in the relevant art. Accordingly, unnecessary details that define medical terminology are not included herein. Also not specifically included are lines/details of computer-programming code which may conventionally be employed by ones skilled in the programming art to implement the two algorithms which are set forth herein in very understandable, high-level, algorithmic terminology and architecture.